1. Field of the Invention
This invention relates to a head unit of a photo detector.
2. Description of the Related Art
Hitherto, a photo detector for irradiating a target area with detection light substantially shaped like a belt and receiving reflected light therefrom to detect a workpiece or the like has been known. FIG. 10(a) shows an example of the structure of a head unit of the photo detector.
In FIG. 10(a), a head unit 100 comprises an alternating pattern of light emission optical fibers 102 and light reception optical fibers 103 arranged in and fixed to a case 101 with an end face exposed.
However, in the related art, a large number of optical fibers 102 and 103 are arranged in the case 101, thus the head unit 100 is upsized.
Since a large number of optical fibers are arranged in a row and fixed to the case 101, the manufacturability of the head unit 100 is poor.
It is therefore an object of the invention to miniaturize a head unit of a photo detector for irradiating a target area with detection light substantially shaped like a belt and receiving reflected light therefrom.
Further, it is another object of the invention to improve the manufacturability of the head unit of the photo detector.
To accomplish the above object, according to a first aspect of the invention, there is provided a head unit of a photo detector for irradiating a target area with detection light having a pencil of rays substantially shaped like a belt in transverse section and receiving light reflected in the target area, the head unit comprising: a light emission section for emitting light to the target area; an optical system for shaping the transverse section form of the pencil of rays from the light emission section into a form substantially shaped like a belt and gathering the light in a direction orthogonal to a length direction in the transverse section of the pencil of rays substantially shaped like a belt for generating detection light substantially shaped like a belt; and a light reception section for receiving the light reflected in the target area and incident on the light reception section through the optical system.
The spot-like light emitted from the light emission section is formed into detection light substantially shaped like a belt by the function of the optical system and the detection light is applied to the target area. The detection light is reflected by an object to be detected or the background in the target area and the reflected light is received at the light reception section through the optical system.
According to a second aspect of the invention, there is provided a head unit of a photo detector for irradiating a target area with detection light having a pencil of rays substantially shaped like a belt in transverse section and receiving light reflected in the target area, the head unit comprising: a belt-like-light generation lens having different light gathering functions relative to two directions orthogonal to each other in the transverse section of the pencil of rays for generating detection light substantially shaped like a belt; a light emission section for emitting the detection light from a first interface of the belt-like-light generation lens through a second interface of the belt-like-light generation lens to the target area; and a light reception section for receiving reflected light incident on the light reception section through the first interface of the belt-like-light generation lens from the second interface.
The spot-like light emitted from the light emission section passes through the belt-like-light generation lens and is formed into detection light substantially shaped like a belt and the detection light is applied to the target area. The detection light is reflected by an object to be detected or the background in the target area and the reflected light passes through the belt-like-light generation lens and is received at the light reception section.
In the invention, a mirror as well as a lens can be used as the xe2x80x9coptical element for gathering lightxe2x80x9d. In the first and second aspects of the invention, more than one lens may be used.
The xe2x80x9coptical systemxe2x80x9d may be made up of two or more optical elements such as a combination of a slit and a lens in addition to a combination of lenses.
The xe2x80x9csubstantially shaped like a beltxe2x80x9d contains not only a shape like a belt or a line, but also an extremely elongated ellipse and the like.
Generally, a bar-like lens such as a cylindrical lens or an elongated plate-like lens can be used as the xe2x80x9cbelt-like-light generation lensxe2x80x9d.
The xe2x80x9clight gatheringxe2x80x9d or xe2x80x9cgathering lightxe2x80x9d refers to making light attempted to spread at a predetermined divergence angle parallel light or making a divergence angle small in addition to converging light. Therefore, the light emitted from a point light source passes through the belt-like-light generation lens and becomes a pencil of rays substantially shaped like an elongated belt.
In addition to the end faces of optical fibers, such elements as LED, LD, and PD can also be used as the xe2x80x9clight emission sectionxe2x80x9d and the xe2x80x9clight reception sectionxe2x80x9d.